Optical thermometry based on level anticrossing in silicon carbide

Band Anticrossing in Dilute Germanium Carbides Using Hybrid Functionals

Dilute germanium carbides (Ge1-xCx) offer a direct bandgap for compact silicon photonics, but widely varying results have been reported. This work uses ab initio simulations with HSE06 hybrid functionals and spin-orbit coupling to study the Ge1-xCx band structure behavior in the absence of defects. Contrary to Vegard's law, the conduction band minimum at k=0 is consistently found to decrease with increasing C content, while L and X valleys change much more slowly. A vanishing bandgap was observed for all alloys with x>0.017. Conduction bands deviate from a constant-potential band anticrossing …

All-optical dc nanotesla magnetometry using silicon vacancy fine structure in isotopically purified silicon carbide

We uncover the fine structure of a silicon vacancy in isotopically purified silicon carbide (4H-$^{28}$SiC) and find extra terms in the spin Hamiltonian, originated from the trigonal pyramidal symmetry of this spin-3/2 color center. These terms give rise to additional spin transitions, which are otherwise forbidden, and lead to a level anticrossing in an external magnetic field. We observe a sharp variation of the photoluminescence intensity in the vicinity of this level anticrossing, which can be used for a purely all-optical sensing of the magnetic field. We achieve dc magnetic field sensiti…

Magnetic field and temperature sensing with atomic-scale spin defects in silicon carbide

Quantum systems can provide outstanding performance in various sensing applications, ranging from bioscience to nanotechnology. Atomic-scale defects in silicon carbide are very attractive in this respect because of the technological advantages of this material and favorable optical and radio frequency spectral ranges to control these defects. We identified several, separately addressable spin-3/2 centers in the same silicon carbide crystal, which are immune to nonaxial strain fluctuations. Some of them are characterized by nearly temperature independent axial crystal fields, making these cente…

Spin and optical properties of silicon vacancies in silicon carbide (a review)

We discuss the fine structure and spin dynamics of spin-3/2 centers associated with silicon vacancies in silicon carbide. The centers have optically addressable spin states which makes them highly promising for quantum technologies. The fine structure of the spin centers turns out to be highly sensitive to mechanical pressure, external magnetic and electric fields, temperature variation, etc., which can be utilized for efficient room-temperature sensing, particularly by purely optical means or through the optically detected magnetic resonance. We discuss the experimental achievements in magnet…

Optical polarization of nuclear spins in silicon carbide

We demonstrate optically pumped dynamic nuclear polarization of 29-Si nuclear spins that are strongly coupled to paramagnetic color centers in 4H- and 6H-SiC. The 99 +/- 1% degree of polarization at room temperature corresponds to an effective nuclear temperature of 5 microKelvin. By combining ab initio theory with the experimental identification of the color centers' optically excited states, we quantitatively model how the polarization derives from hyperfine-mediated level anticrossings. These results lay a foundation for SiC-based quantum memories, nuclear gyroscopes, and hyperpolarized pro…

基于碳化硅中自旋-3/2中心精细与超精细相互作用的全光扫描矢量磁力测量

All-optical scanning vector magnetometry based on fine and hyperfine interactions in spin-$\frac{3}{2}$ centers in silicon carbide

提出利用4H-SiC中S=3/2自旋色心的LAC谱随磁场取向变化，实现无需微波、可基于单个中心的全光扫描矢量磁力测量。